Condition responsive control



March O16, '1943.

G. M. HAUSLER 2,314,210

CONDITION RESPONSIVE CONTROL Filed sept. ze, 1941 Inventor: George M.Husler,

His ACtofrwe y.

Patented Mar. 16, 1943 2,314,210 CONDITION RESPONSIVE CONTROL George M.Hausler, Ballston Lake, N. Y., assigner to General Electric Company, acorporation of New York Application september ze, 194i, serial No.412,415

13 Claims. The invention relates to condition responsive control,particularly condition responsive control switches operable with adifferential in response to variations in a predetermined controlcondition such as pressure, temperature or the like.

One of the principal objects is to provide an improved conditionresponsive switch Calibrating mechanism with improved means foradjusting the differential of operation independently of the switch.

A more specic object is to provide an improved condition responsivevariable differential calibrating mechanism for a switch unit having theprincipal operating parts of a reversely biased main and differentialadjusting mechanism mounted in nested overlapping cooperating relationwithin a channel frame in cooperating relation with a movableCalibrating scale and movable pointer, and having the switch unitmounted in parallel offset side-by-side alignment with the channel frameto enable the switch unit and its adjustable Calibrating mechanism to bemounted' on the opposite side of a base plate from the conditionresponsive operating device therefor so as to obtain a more accurate,compact and stronger mechanical construction. This is particularlyadvantageous where relatively heavy operating forces are encountered asfor example in a steam pressure responsive control.

A more general object is to provide an improved condition responsivevariable diierential control calibrating mechanism whereby the differentvalues of the control condition required to operate the control betweentwo control positions may each be indicated directly' on a movablecalibrating scale and each adjusted at will.

Other objects and advantages of the present invention will becomeevident in the following description of the accompanying drawing inwhich Fig. l is a side view of a pressure responsive switch embodyingthe invention in a preferred form with the cover broken away moreclearly to reveal the internal construction; Fig. 2 is a sectional viewof the pressure switch taken from the end on the line 2--2; Fig. 3 is asectional view of the pressure switch taken from the side on the line3-3 and Fig.'4 is a sectional l of moulded insulating material, has theinternal ribs I1 engaging with the upturned rim Ia and is provided withsuitable end openings I6 for receiving the end plates II. Cover I5isheld in place by screw I8 which engages with the threaded socket I9carried by the main channel frame adjustable differential calibratingunit 20 within which all of the parts of the switch Calibratingmechanism are mounted in cooperating relation. A window opening 2l isformed in the top of cover I5 in order to permit observation of thesetting of the improved calibrating scale mechanism with which thechannel frame adjustable differential Calibrating unit 20 is provided asdescribed hereinafter.

The main channel frame adjustable differential Calibrating unit 20 isprovided with corner lugs 22 which fit into corresponding slots formedin the base I0 in order to secure the frame accurately in properposition on the base bythe screws 23. A pivot pin 21 extends across oneend of the channel frame 20 for mounting the main L-shaped operatinglever 28 with the longer arm 28a thereof extending in substantiallyparallel spaced apart relation with the base I0 and with the shorter arm28h extending upwardly at right angles. The mainlever arm 28a isprovided with the upturned stiiening side channels 29 with bearingopenings therein for receiving the pivot pin 21. 'Ihe main lever arm28av has an offset finger 30 extending through an opening 3| formed inone side of the channel frame 20 so as to move in the space under theauxiliary L-shaped mounting frame 35 which is secured to the base Iiiand to the main frame 20 by means of lugs similar to lugs 22 and thescrew 34.

A sealed snap switch mechanism 36 is mounted upon the auxiliary frame 35with its operating pin 31 extending into operating relation with thefinger 30 of the main operating lever 3B. This sealed snap switchmechanism as shown is of the improved type described and claimed inthevcopending application, Serial No. 463,474, filed July 22, 1941, andassigned to the assignee of the present invention, although any othersuitable type of snap switch mechanism may be employed, if desired.

In the snap switch mechanism 36, as shown, the operating pin 31 extendsthrough the enclosing casing and operates the main pivoted switchoperating lever 38 through the agency of the spring strip 39 carried bythe main pivoted lever 38. The movable switch contact is carried on themain operating lever 38 so as to engage with a cooperating stationarycontact when the main lever 38 is in engagement with the adjustable stop48. A permanent magnet 4l is provided for biasing lever 38 intoengagement with stop 48 so as to effect snap action of the movableswitch contact, to and from the circuit closing position. Since thedetailed construction of the snap action switch mechanism itself is notof the essence o! the present invention, no further description thereofis deemed necessary as any suitable form of snap switch may be employed.

The main L-shaped switch operating lever 28 is actuated by an operatingpin 58 which extends through the opening I8b in base plate I8. Pin 58 inturn is operated by the pressure responsive bellows 52 enclosed withinthe sealed casing 53. The casing 53 is provided with a screw threadedconnecting` plug 54 for connection to a boiler or other source ofpressure to which the bellows 52 is thus made responsive. A biasingforce, opposing the action of bellows 52 on lever 28, is provided by themain pressure Calibrating spring 68 which is secured at its ends to thethreaded plugs 6|, 62, the latter having an arm 82a extending upwardlythrough a slot 83 formed in the channel frame 28. A factory calibratingscrew 65 extends through an opening formed in the end of the arm 28hinto threaded engagement with the lug 6|. A main pressure adjustingscrew 88 extends through a cross bar 81 into threaded engagement withthe plug 82. The cross bar 81 is mounted in the dovetailed slots 88formed in the *opposite legs of the channel frame 28 and is arranged tobe locked in place by wedging apart the bendable portions 61a of thecross bar 81.

After the factory calibration is completed, the screw 65 is locked,preferably by soldering. so that all further adjustment of the tensionof the spring 68 is accomplished by turning the screw 56 so as to varythe position of the threaded lug 62. Thus the biasing force of the mainspring 60 will vary with the setting of the screw plug 82 and determinethe pressure value at which the pivoted arm 28 is operated to move thesnap action switch mechanism 38 to one of its controlled positions,namely, the circuit closing position.

The setting of the main calibratlng spring 68 is indicated by stationarypointer 89 cooperating with the movable calibration scale 18 whichslides in the upturned guides 1| formed in the top of the channel frame28. The scale 18 is shown in Fig. 4 as calibrated for the pressurecontrol range over which the pressure switch may be adjusted to operateand is moved by the arm 82a in accordance with the position of the screwplug 82 which, in turn, is determined by the adjustment of the mainadjusting screw 88. In this way the lower limit of the pressure controlrange is always indicated by the stationary pointer 83 on thereciprocating pressure calibrated scale 18.

Dilerential adjustment Variation in the operating di'erential o! themechanism is obtained by means of the complementary reversed overlappingL-shaped calibrating lever which is provided with the enlarged opening16e around the screw 88 and is pivotally mounted upon the pin 18extending across the channel frame 28 adjacent the end opposite the mainpivot pin 21. The diiferential adjusting lever 15 is provided with arounded finger 11 at the end of the longer arm 15a so as to be in thepath of and engage with the slightly raised platform 18 formed on thearm 28a oi the main operating lever 28. However, when the arm 28a is inthe position shown in which the switch 38 is closed, the linger 11 ismaintained out of engagement with the platform 18 due to the fact thatthe finger 18 laterally extending from arm 15a engages with the stop 88provided in the side wall of the channel frame 28. The L-shapeddifferential lever 15 is biased into engagement with stop 88 by thediierential adjustment spring 83 which is mounted in superimposedparallel relation with the main spring 88 inside of channel frame 28 inthe space between the upturned arms of the two superimposed overlappingL-shaped levers 28 and 15. 'I'he differential calibrating spring 83,similarly to the main spring 58, is-

provided with the threaded plugs 84 and 85 at its ends.V Plug 84 is inthreaded engagement with the factory adjustment screw 88 which extendsthrough a suitable opening adjacent the end of the shorter upright arm15b of the differential calibrating lever 15 and the plug 85 is inthreaded engagement with the diierential adjustment screw 81.l Thisdiilerential adjustment screw 81 is mounted in the-cross bar 88 which inturn is mounted in the dovetailed grooves 89 formed in the ends of thechannel frame 28 and anchored in place in exactly the same way as thecross bar 81 by wedging apart the bendable sections 88a. After theproper factory differential adjustment is made, the factory adjustingscrew 88 is locked in position, preferably by soldering. Thereafteradjustment of the differential spring 83 is accomplished entirely byturning the differential adjusting screw 81 so as to vary the positionof the threaded lug 85 and thereby vary the tension exerted by thedifferential spring 83 on the differential lever 15.

The setting of the differential spring 83 is indcated by the movablepointer 38 which is carried by and extends upwardly from the threadedplug 85 through the slot 9| formed in the upper side of the channelframe 28 adjacent to the edge of the sliding scale 18, as shown moreclearly in Fig. 4.

The relative proportions of all the parts are such that the joint actionof the main pressure calibrating spring 88 and the diil'erential spring83 determine the pressure value required to effect operation of the snapaction switch 38 from the closed position to the open position. This isdue to the fact that the setting of the spring 88 alone determines thevalue at which the switch is operated to the closed position but theadded force of difleretnial spring 83 determines the pressure value atwhich the switch is operated to the open position. This switch openingpressure value is indicated directly on the movable scale 18 by themovable pointer 98, the position of which will vary in accordance withthe adjustment of the tension of the diierential spring 83. In this waythe upper limit of the pressure control range is always indicated by themovable pointer 90 on the reciprocating pressure calibrated scale 18.

Operation With the parts of the improved condition responsive controlswitch in their relative positions as shown, the contacts of switch- 36are closed and the operation is as follows:

When the pressure within casing 53 increa es, the bellows 52 iscompressed and moves the operating pin 58 upwardly thereby rotating themain lever 28 about the pivot pin 21 so as to .raise the lateralextending arm 38 and thereby move the switch operating pin 31 upwardlyto build up a force in the switch operating spring strip 39 tending toeffect snap action operation of the switch contact from the closedposition to the open position. During the initial movement of the mainlever 28, only the main spring 68 opposes the operating force of thebellows 52, but as soon as arm 28 has moved upwardly a sufiicientdistance to engage the platform 18 with the finger 11, then the force ofthe differential spring 83 is added to that of the main spring 60 inopposition to the pressure exerted on the bellows 52. Thus the pressuremust increase to a value sufficient to overcome both main spring 60anddifferential spring 83, before CII 1. A `condition responsive controlhaving in y combination, a base plate with an opening formed therein,condition responsive means mounted on one side of said, plate and havingan` operating member extending through saidv v opening, achannel framemounted on the opthe lateral finger 30 will move the pin 31 upeffectiveto operate the main pivot lever 28 against the opposing force of thebellows 52 so as to lower the laterally extending arm 30. However,before the switch operating pin 31 has been lowered sufliciently toeffect snap action operation of the switch 36 to the circuit closingposition, the laterally extending arm 80 on the differential lever 15engages with the stop 19 thereby preventing the force of thedifferential spring 83 from opposing the force of the bellows 52.Consequently the pressure within the casing 53 must then decrease to avalue sufficiently low that the main spring 60 can move the platform 18out of engagement with the finger 11 thereby lowering the laterallyextending arm sufliciently to permit 'snap action closure of the switch36. Thus the closure of the switch is determined solely by theadjustmentl of the main spring 60, and the setting of the main springEl) is indicated on the moving scale 10 by the stationary pointer 69.

The main adjusting screw 66 may be operated so as to `move the scale 'l0to the particular pressure value at which it is desired that the switch36 be operated to the circuit closing position. The length of slot 63limits this movement, Likewise the differential adjusting screw 81 maybe rotated to move the pointer 98 so as to indicate the desiredhigherpressure value at which the switch 36 will be operated to thecircuit opening position. The length and relative position of slot 9|limits this movement.

. It will be understood that, if desired, the switch 36 may be arrangedto open its contacts at the pressure value determined by the adjustmentof the main spring 66 and to close its contacts at the pressure valuedetermined bv the adjustment of the differential spring 81, if desired.

posite side of said plate to straddle said member andhaving an openingin one side thereof, an L-shaped main operating lever pivotally mountedwithin and 'adjacent one end of said channel frame with one arm thereofengaging said operating member to be operated thereby and having afinger extending laterally through said side opening in said channelframe, a reversed L-shaped differential control lever pivotally mountedwithin' and adjacent the opposite end of said channel frame with one armdisposed in the path of the said one arm of said main lever, a pair ofcalibrating springs reversely mounted within said channel frame insubstantially parallel spaced apart alignment between the other arms ofsaid L-shaped levers and each having one end thereof connected to acorresponding one of said other arms and a tension adjusting elementconnected to the opposite end thereof, a Calibrating scale elementmovably mounted on said channel frame and secured to and movable withthe said tension adjusting element of said main lever calibratingspring, a stationary pointer mounted on said frame and cooperating withlsaid movable scale member to indicate the calibration of said mainleverI Calibrating spring, a second indivati-ng relation with eatingpointer secured to and movable with the said tension adjusting member ofsaid differential lever Calibrating spring for independently indicatingthe joint calibration thereof on said scale and acircuit controllingswitch ,unit mounted cn said base in off set side-by-side alignment withsaid channel frame and in opersaid laterally extending finger of saidmain operating lever.

2. A condition responsive control having in combination. a base platewith an opening formed therein. a condition responsive device having anoperating member extending through said opening, a channel frame mountedon said plate to straddle said member, main lever pivotally mountedwithin and adjacent one end of said channel frame with said leverengaging said member to`be operated thereby, a differential controllever pivotally mounted within and adjacent the opposite end ofsaidchannel frame and disposed in the path of said main lever, a pair ofreversed parallel Calibrating springs mountedwithin said channel frameand each Also other forms of condition responsive del having one endthereof connected to a. corresponding one of said levers and a tensionadjusting element connected to the opposite end therelof, a movableCalibrating scale element secured to and movable with the said adjustingelement of said main lever Calibrating spring, a stationary pointercooperating with said movable scale member to indicate the calibrationof said main lever Calibrating spring, a second indicating pointersecured to and movable with said tension adjusting member of saiddifferential lever calibrating spring for independently indicating thejoint calibration thereof on said scale and a circuit controlling switchmcunted on said base to be operated by said main operating lever.

3. A condition responsiveeontrol having `in combination, a conditionresponsive device having an operating member, a channel frame straddlingsaid member, a main lever pivotally mounted within and adjacent one endof said channel frame to be engaged by said member, a diilerentialcontrol lever pivotally mounted within and adjacent the other end ofsaid channel frame and disposed in the path of said main lever, a pairof reversed parallel Calibrating springs mounted within said channelframe and each having one end thereof connected to a corresponding oneof said levers and a tension adjusting element connected to the oppositeend thereof, a movable calibrating scale element secured to and movablewith the said adjusting element of said main lever calibrating spring, astationary pointer cooperating with said movable scale member toindicate the calibration of said main lever calibrating spring, a secondindicating pointer secured to and movable with said tension adjustingmember of said differential lever calibrating spring for independentlyindicating the joint calibration thereof on said scale and a circuitcontrolling switch operated by said main operating lever member.

4. A condition responsive control having in combination, a conditionresponsive device having a main movable control member operated therebybetween two control positions, a movable differential control memberdisposed in the path of said main control member between said positions,a separate calibrating spring for each member, each spring having oneend thereof connected to the corresponding member and a tensionadjusting element connected to the opposite end thereof, a movablecondition calibrated scale element secured to and movable with the saidtension adjusting element of said main calibrating spring, a stationarypointer cooperating with said movable scale member to indicate the valueof the condition to which said device is responsive required to eiectoperation of said main control member to one of said positions, and asecond indicating pointer secured to and movable with said tensionadjusting member of said differential calibrating spring forindependently indicating on said scale the value of the condition towhich said device is responsive required to eil'ect operation of saidmain control member to the other of said positions.

5. A condition responsive control having in combination, a conditionresponsive element, variable differential control means operated by saidelement upon variation in the condition to which said element isresponsive over an operating range having variable limits, a rangecalibrating spring for said control means, a differential Calibratingspring for said control means, each of said springs having an adjustingmember, a movable calibrating scale element connected for movement withthe said adjusting element of said range spring, a pointer cooperatingwith said movable scale member to indicate one limit of the operatingrange of said control means, and a movable indicating pointer connectedfor movement with said adjustingmember of said difierential spring forindependently indicating the other limit oi' the operating range of saidcontrol means on said scale.

6. A condition responsive device having in combination conditionresponsive operating means, switching means operated by said responsivemeans between two positions upon variation in the condition to whichsaid operating means is responsive over an operating range havingvariable limits, a pair of adjustable biasing means. one of said biasingmeans acting on said kswitching means in the other position, andcalibrating means including a stationary pointer and a cooperatingmovable scale connected to be moved in accordance with the adjustment oisaid one biasing means for indicating one limit of the operating rangeoi said operating means and having a movable pointer cooperatingtherewith and connected to be moved in accordance with the adjustment ofsaid other biasing means for indicating the other limit of the operatingrange of said operating means.

7. A condition responsive device having in combination conditionresponsive operating means, a movable control member operated therebybetween two positions upon variation in the condition to which saidoperating means is responsive over an operating range having variablelimits, means including a pair of adjustable biasing means for varyingsaid limits, one of said biasing means acting on said conditionresponsive means with said member in one of said positions and both ofsaid biasing means acting on said responsive means with said member inthe other of said positions, and Calibrating means including astationary pointer and a cooperating movable condition calibrated scaleconnected to be operated in accordance with the adjustment of said onebiasing means for indicating one limit of the operating range of saidoperating means and having a movable pointer cooperating therewith andconnected to be moved in accordance with the adjustment of said otherbiasing means for indicating the other limit of the operating range ofsaid operating means.

8. A condition responsive device having in combination a channel frame,a pair of L-shaped levers mounted Within said channel frame in reversedoverlapping relation with one arm oi' one of said members disposed inthe path of movement of the corresponding arm of the other of saidlevers, a pair of reversed parallel Calibrating springs mounted withinsaid channel frame in the space between the other arms of said members,and each having one end thereof connected to a corresponding one of saidother arms, a pair of adjusting means each connected with the other endof a corresponding one oi said springs, a condition responsive devicehaving an operating member engaging said one arm of said one lever,

Aand a switch mounted to be operated by said one mounted in the spacebetween the other arms combination a channel frame having a barextending across each end thereof, a pair of springs mounted within saidchannel frame and each adjustably connected with a corresponding bar, a

pair of L-shaped levers pivotally mounted within said channel frame inreversed overlapping relation and each connected with a correspondingspring, condition responsive means for operating one of said levers intoengagement with the other lever, and a switch mounted to be operated bysaid one lever to one position in accordance with the adjustable .biasof the corresponding spring and to a second position in accordance withthe adjustable bias of both of said springs.

11. A 'condition responsive device having in combination a base providedwith an opening, a channel frame calibrating unit mounted on one side ofsaid base to straddle said base opening and having an opening in oneside thereof, lever mechanism pivotally mounted within said frame andhaving a finger extending through said side opening, a conditionresponsive device mounted on the opposite side of said base and havingan operating member extending through said base opening for operatingsaid lever ,mechanism, and a switch mounted on said base adjacent saidone side of said channel frame to 'be operated by said finger.

12. A condition responsive device having in combination a channel frameCalibrating unit provided with an opening in one side thereof, levermechanism pivotally mounted Within said frame and having a ngerextending through said opening, a condition responsive device having amovable operating member extending between the edges of said channel foroperating said lever mechanism, and a switch mounted at said one side ofsaid channel frame to be operated by said finger.

13. In combination, a variable differential ccndition responsive controldevice having a differential adjusting screw and a separately operable'control range adjusting screw disposed in parallel alignment, areciprocating calibrated control range scale having a threaded drivingelement operated by said range adjusting screw, a stationary pointerdisposed at one side of said scale for indicating thereon one limit ofthe control range of said device, and a movable pointer having athreaded driving element operatedtby said diil'erential adjusting memberfor moving said pointer along the other side of said scale to indicatethereon the other limit of said control fange.

GEORGE M. HAUSLER.

